An analog switch circuit is used for switching an analog signal. Regarding characteristics of an analog switch circuit that is used in a signal path of an analog signal, it is noted that ON-resistance of a switch can distort a signal waveform.
Japanese Laid-open Patent Publication No. 2008-35153 describes a conventional circuit that maintains a constant ON-resistance. However, the circuit is not effective for low frequency signals. There is also a drawback of the conventional circuit in that ON-resistance may not be sufficiently reduced because only up to ½ VDD is applied between a gate and a source or drain in the conventional circuit.
IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 34 No. 5, MAY 1999 “A 1.5-V, 10-bit, 14.3-MS/s CMOS Pipeline Analog to Digital Converter” discusses a conventional bootstrap circuit that maintains ON-resistance of a sampling switch constant. However, this conventional circuit may not operate continuously because it repeats ON and OFF operations. Accordingly, the conventional bootstrap circuit is not suitable for using as an analog switch. In other words, the conventional bootstrap circuit configuration does not support continuous signals with low frequency, and is not for practical as an analog switch.